A method and a device made according to the method. The method comprises providing a substrate including a first material, and providing a fin including a second material, the fin being disposed on the substrate and having a device active portion, the first material and the second material presenting a lattice mismatch between respective crystalline structures thereof. Providing the fin includes providing a biaxially strained film including the second material on the substrate; and removing parts of the biaxially strained film to form a substantially uniaxially strained fin therefrom.
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1. A device, comprising:
a substrate including a first material;
a uniaxially strained fin including a second material, the fin being disposed on the substrate and having a device active portion;
wherein the first material and the second material present a lattice mismatch between respective crystalline structures thereof;
wherein a source region and a drain region, both included in the fin and both including the second material, have greater lattice mismatch with the first material than other regions of the fin.
11. A method of making a device comprising:
providing a substrate including a first material;
providing a fin including a second material, the fin being disposed on the substrate and having a device active portion, the first material and the second material presenting a lattice mismatch between respective crystalline structures thereof, wherein providing the fin includes:
providing a biaxially strained film including the second material on the substrate; and
removing parts of the biaxially strained film to form a substantially uniaxially strained fin therefrom;
wherein a source region and a drain region, included in the fin and including the second material, have greater lattice mismatch with the first material than other regions of the fin.
2. The device of
a gate dielectric on the device active portion;
a gate electrode on the gate dielectric.
3. The device of
4. The device of
6. The device of
7. The device of
the device active portion includes:
the source region adjacent one side of the gate electrode;
the drain region adjacent another side of the gate electrode opposite the one side;
wherein the fin includes a third material at each of the source region and the drain region, the third material presenting a lattice mismatch between a crystalline structure thereof and the crystalline structure of the first material which is greater than the lattice mismatch between respective crystalline structures of the second material and of the first material.
8. The device of
the first material comprises silicon;
the second material comprises an alloy of silicon and a strain inducing element; and
the second material at the source region and at the drain region contains a higher percentage of the strain inducing element than at other regions of the device active portion.
10. The device of
12. The method of
providing a gate dielectric on the device active portion; and
providing a gate electrode on the gate dielectric.
13. The method of
14. The method of
15. The method of
17. The method of
providing the source region in the device active portion adjacent one side of the gate electrode;
providing the drain region in the device active portion adjacent another side of the gate electrode opposite the one side;
wherein the fin includes a third material at each of the source region and the drain region, the third material presenting a lattice mismatch between a crystalline structure thereof and the crystalline structure of the first material which is greater than the lattice mismatch between respective crystalline structures of the second material and of the first material.
18. The method of
the first material comprises silicon;
the second material comprises an alloy of silicon and a strain inducing element; and
the second material at the source region and at the drain region contains a higher percentage of the strain inducing element than at other regions of the fin.
19. The method of
20. The method of
recessing the device active portion at said one side and at said another side of the gate electrode to define respective recesses; and
providing the source region and the drain region within the respective recesses such that the source region and the drain region include a higher percentage of the strain inducing element than other regions of the device active portion.
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Microelectronic integrated circuits, such as microprocessors, comprise literally hundreds of millions of transistors. The speed of the integrated circuits is primarily dependent on the performance of these transistors. Thus, the industry has developed unique structures, such as non-planar transistors, and the use of straining techniques on components within the transistors to improve performance.
The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. It is understood that the accompanying drawings depict only several embodiments in accordance with the present disclosure and are, therefore, not to be considered limiting of its scope. The disclosure will be described with additional specificity and detail through use of the accompanying drawings, such that the advantages of the present disclosure can be more readily ascertained, in which:
In the following detailed description, reference is made to the accompanying drawings that show, by way of illustration, specific embodiments in which the claimed subject matter may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the subject matter. It is to be understood that the various embodiments, although different, are not necessarily mutually exclusive. For example, a particular feature, structure, or characteristic described herein, in connection with one embodiment, may be implemented within other embodiments without departing from the spirit and scope of the claimed subject matter. In addition, it is to be understood that the location or arrangement of individual elements within each disclosed embodiment may be modified without departing from the spirit and scope of the claimed subject matter. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the subject matter is defined only by the appended claims, appropriately interpreted, along with the full range of equivalents to which the appended claims are entitled. In the drawings, like numerals refer to the same or similar elements or functionality throughout the several views, and that elements depicted therein are not necessarily to scale with one another, rather individual elements may be enlarged or reduced in order to more easily comprehend the elements in the context of the present description.
Embodiments of the present description relate to the fabrication of microelectronic devices. In at least one embodiment, the present subject matter relates to forming isolation structures in semiconductor bodies of non-planar transistors.
In the fabrication of non-planar transistors, such as tri-gate transistors, FinFETs, omega-FETs, and double-gate transistors, non-planar semiconductor bodies may be used to form transistors capable of full depletion with very small gate lengths (e.g., less than about 30 nm). For example in a tri-gate transistor, the semiconductor bodies generally have a fin-shape with a top surface and two opposing sidewalls formed on a bulk semiconductor substrate or a silicon-on-insulator substrate. A gate dielectric may be formed on the top surface and sidewalls of the fin and a gate electrode may be formed over the gate dielectric on the top surface of the fin and adjacent to the gate dielectric on the sidewalls of the fin. Thus, since the gate dielectric and the gate electrode are adjacent to three surfaces of the fin, three separate channels and gates are formed. As there are three separate channels formed, the fin can be fully depleted when the transistor is turned on.
Semiconductor bodies are generally formed of silicon-containing materials, and, as will be understood to those skilled in the art, inducing strain in silicon-containing materials can enhance channel mobility. An increase in channel mobility can result in advantages, including but not limited to, reduced electrical resistance, improved efficiency, increased current, and increased speed. Strain may be induced on a fin by materials that have lattice mismatch (e.g. a different lattice constant or size) in their crystalline structures. For example, when silicon and a silicon alloy including a strain inducing element therein, such as, for example germanium (where the alloy includes silicon germanium), are used to the form the substrate and the fin, respectively, the difference in lattice parameter between the silicon and the silicon alloy can cause the silicon alloy to be strained. Epitaxially grown strained silicon germanium is one example of a strained film grown on a silicon substrate. A silicon germanium film may otherwise be provided according to any one of well known methods, such as, for example, CVD, PVD, MBE, or any other suitable thin film deposition process.
Embodiments encompass an alloy of any strain inducing element with a semiconductor material that may result in a lattice mismatch with the material of the substrate. Thus, a strain inducing “element” as noted herein is not necessarily limited to a pure element from the periodic table of elements, but could include any material that, when alloyed with a semiconductor material, causes the lattice mismatch as noted above. For example, where the substrate is made of silicon, carbon and silicon may be used together to form a SiC alloy that would result in a tensile strain in the fin by virtue of a lattice mismatch with the silicon substrate, versus a compressive strain brought about by silicon germanium. SiC may for example be provided on the substrate according to the same methods as described in the paragraph above for silicon germanium. Other examples of strain inducing elements according to embodiments may include phosphorus, boron, nitrogen or tin.
Each transistor 100, shown as tri-gate transistors, includes a semiconductor body 110 defining a fin 112, the semiconductor body 110 being formed adjacent the substrate active region 106. The fin 112 includes a device active portion 113 which extends above a surface of isolation regions 104. Device active portion 113 may have a top surface 114 and a pair of laterally opposite sidewalls, sidewall 116 and opposing sidewall 118. Semiconductor body 110 may be formed from a material, such as a single crystalline semiconductor having a different lattice constant or size than the bulk semiconductor substrate 102 so that semiconductor body 110 has a strain induced therein. In one embodiment of the present disclosure, the semiconductor substrate 102 is a monocrystalline silicon substrate and the semiconductor body 110 is a single crystalline silicon germanium alloy.
As further shown in
The gate dielectric layer 134 may be formed from any well-known gate dielectric material, including but not limited to silicon dioxide (SiO2), silicon oxynitride (SiOxNy), silicon nitride (Si3N4), and high-k dielectric materials such as hafnium oxide, hafnium silicon oxide, lanthanum oxide, lanthanum aluminum oxide, zirconium oxide, zirconium silicon oxide, tantalum oxide, titanium oxide, barium strontium titanium oxide, barium titanium oxide, strontium titanium oxide, yttrium oxide, aluminum oxide, lead scandium tantalum oxide, and lead zinc niobate. The gate dielectric layer 134 can be formed by well-known techniques, such as by depositing a gate electrode material, such as chemical vapor deposition (“CVD”), physical vapor deposition (“PVD”), atomic layer deposition (“ALD”), and then patterning the gate electrode material with well-known photolithography and etching techniques, as will be understood to those skilled in the art.
As shown in
The “width” of each tri-gate transistor in
The gate electrode 136 can be formed of any suitable gate electrode material. In an embodiment of the present disclosure, the gate electrode 136 may be formed from materials that include, but are not limited to, polysilicon, tungsten, ruthenium, palladium, platinum, cobalt, nickel, hafnium, zirconium, titanium, tantalum, aluminum, titanium carbide, zirconium carbide, tantalum carbide, hafnium carbide, aluminum carbide, other metal carbides, metal nitrides, and metal oxides. The gate electrode 136 can be formed by well-known techniques, such as by blanket depositing a gate electrode material and then patterning the gate electrode material with well-known photolithography and etching techniques, as will be understood to those skilled in the art.
Referring still to
The greater lattice mismatch described above may be achieved in a number of different ways. For example according to one embodiment, recessed regions may be defined in the fin at locations where source and drain regions are to be provided. For example, the fin may be subjected to etching techniques to provide recessed therein as would be recognized by one skilled in the art. The etch of the source drain recesses may be effected for example in a self-aligned manner by aligning the source/drain recess etch to the gate electrode stack and spacers of the multi-gate device. Thereafter, the material for the source and drain regions may be epitaxially re-grown into the recesses. The material for the source and drain regions may for example include a doped material and/or a material including the same percentage of the strain inducing element as that present in the rest of the fin. For example, where the fin material includes a silicon germanium alloy, the source and drain recesses may be refilled with a doped silicon germanium alloy and/or with a silicon germanium alloy having the same percentage of germanium as present in the rest of the fin. The silicon germanium could for example be doped with boron or with any other similar dopant as would be recognized by one skilled in the art. Where the fin material includes SiC, a dopant choice could include, for example, phosphorus, as would be recognized by one skilled in the art.
According to another embodiment, more of the strain inducing element may be implanted into the material of the fin by way of ion doping in order to impart further strain to the fin at the source and drain regions, thus avoiding a need to provide recesses in the source and drain regions. In such an instance, the source and drain regions would exhibit higher doping levels than other regions of the fin. For example, the dopant could include boron or any other similar dopant as would be recognized by one skilled in the art. Examples of dopants according to embodiments could include germanium to increase strain, or boron to improve resistance, other dopants being within the purview of embodiments.
Referring next to
Referring next to
Referring next to
As seen in
Referring more particularly to
Referring first to
As seen in
The percentage of the strain inducing element may be chosen to optimize transistor performance, as will be understood to those skilled in the art. For example, where the strain inducing element comprises germanium, the material of the fin may between about 30% and about 70% germanium, and preferably between about 40% to about 50% germanium. Optionally, the material of the fin may have a constant percentage of the strain inducing element throughout a volume thereof extending between substrate and the gate dielectric. For example, referring to
Referring to Table 1 below, a comparison is provided of measured and simulated strain averages before and after etching of SiGe film containing 40% germanium.
TABLE 1
Average of
Average of
average biaxial
average biaxial
strain measured
strain in SiGe
by Raman
from Simulation
Before etching
−1.60%
−1.55%
After etching
−0.85%
−0.80%
The measured averages of averages were obtained by using actual and simulated Raman spectroscopy for a SiGe film. The averages of averages were obtained by using Raman spectroscopy measurements and Finite element based stress simulations for a SiGe film. As suggested in the first column of Table 1, the strain in the SiGe film is less after etching than before etching. The second column of Table 1, relating to simulated data for a biaxially strained SiGe film, strongly correlates with the values in column one, and suggests that that the biaxial strain is relaxed to uniaxial post etching.
Referring next to
Referring next to
The drawings and the forgoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions any flow diagram need not be implemented in the order shown; nor do all of the acts necessarily need to be performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of embodiments is at least as broad as given by the following claims.
Kavalieros, Jack T., Giles, Martin D., Ghani, Tahir, Kuhn, Kelin J., Kotlyar, Roza, Zelick, Nancy M., Cea, Stephen M., Kuhn, Markus
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